1 files changed, 57 insertions, 1 deletions
diff --git a/lib/libsys/kqueue.2 b/lib/libsys/kqueue.2
index d6e949baa24c..e413f7d4fbca 100644
--- a/lib/libsys/kqueue.2
+++ b/lib/libsys/kqueue.2
@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd March 26, 2023
+.Dd September 4, 2025
 .Dt KQUEUE 2
 .Os
 .Sh NAME
@@ -593,6 +593,62 @@ returns the number of times the signal has occurred since the last call to
 This filter automatically sets the
 .Dv EV_CLEAR
 flag internally.
+.It Dv EVFILT_JAIL
+Takes the jail ID to monitor as the identifier and the events to watch for
+in
+.Va fflags ,
+and returns when the jail performs one or more of the requested events.
+If a process can normally see a jail, it can attach an event to it.
+An identifier of zero will watch the process's own jail.
+The events to monitor are:
+.Bl -tag -width "Dv NOTE_JAIL_ATTACH"
+.It Dv NOTE_JAIL_SET
+The jail has been changed via
+.Xr jail_set 2 .
+.It Dv NOTE_JAIL_ATTACH
+A process has attached to the jail via
+.Xr jail_attach 2
+or a similar call.
+The process ID will be stored in
+.Va data .
+If more than one process has attached since the last call to
+.Fn kevent ,
+.Va data
+will contain the most recently attached process ID,
+with
+.Dv NOTE_JAIL_ATTACH_MULTI
+set in
+.Va fflags .
+.It Dv NOTE_JAIL_REMOVE
+The jail has been removed.
+.It Dv NOTE_JAIL_CHILD
+A child of the watched jail has been created.
+.It Dv NOTE_TRACK
+Follow child jails created under this jail.
+Register a new kevent to monitor the child jail using the same
+.Va fflags
+as the original event.
+The child jail will signal an event with
+.Dv NOTE_CHILD
+set in
+.Va fflags
+and the parent JID in
+.Va data .
+.Pp
+If registering a new kevent fails
+.Pq usually due to resource limitations ,
+it will signal an event with
+.Dv NOTE_TRACKERR
+set in
+.Va fflags ,
+and the child jail will not signal a
+.Dv NOTE_CHILD
+event.
+.El
+.Pp
+On return,
+.Va fflags
+contains the events which triggered the filter.
 .It Dv EVFILT_TIMER
 Establishes an arbitrary timer identified by
 .Va ident .